title: Magnetic excitations of Fe(1+y)Se(x)Te(1-x) in magnetic and superconductive phases.
abstract: We have used inelastic neutron scattering and muon-spin rotation to compare the low energy magnetic excitations in single crystals of superconducting Fe(1.01)Se(0.50)Te(0.50) and non-superconducting Fe(1.10)Se(0.25)Te(0.75). We confirm the existence of a spin resonance in the superconducting phase of Fe(1.01)Se(0.50)Te(0.50), at an energy of 7 meV and a wavevector of (1/2, 1/2, 0). The non-superconducting sample exhibits two incommensurate magnetic excitations at (1/2, 1/2, 0) ± (0.18, - 0.18, 0) which rise steeply in energy, but no resonance is observed at low energies. A strongly dispersive low energy magnetic excitation is also observed in Fe(1.10)Se(0.25)Te(0.75) close to the commensurate antiferromagnetic ordering wavevector (1/2 - δ, 0, 1/2), where δ≈0.03. The magnetic correlations in both samples are found to be quasi-two-dimensional in character and persist well above the magnetic (Fe(1.10)Se(0.25)Te(0.75)) and superconducting (Fe(1.01)Se(0.50)Te(0.50)) transition temperatures.
authors.affiliation: Department of Physics, Clarendon Laboratory, Oxford University, Oxford OX1 3PU, UK. peter.babkevich@physics.ox.ac.uk
authors.forename: P
authors.initials: P
authors.lastname: Babkevich
authors.forename: M
authors.initials: M
authors.lastname: Bendele
authors.forename: A T
authors.initials: AT
authors.lastname: Boothroyd
authors.forename: K
authors.initials: K
authors.lastname: Conder
authors.forename: S N
authors.initials: SN
authors.lastname: Gvasaliya
authors.forename: R
authors.initials: R
authors.lastname: Khasanov
authors.forename: E
authors.initials: E
authors.lastname: Pomjakushina
authors.forename: B
authors.initials: B
authors.lastname: Roessli